Sir Edmund Hillary has backed the preservation of Sir Ernest Shackleton's hut in the Antarctic - because of an eerie encounter with the British pioneer's phantom.

Conservation work begun last week on the Nimrod hut, overlooking a bay at Cape Royds, Ross Island, has spirited significance for Sir Edmund, who described seeing an apparition when he first visited.

In a video promoting the project, the patron of the Antarctic Heritage Trust said it was an experience that had a profound effect on him.

"I'm not a person who really sees things very much but when I opened the door I distinctly saw Shackleton walking towards me and welcoming me," he said.

"It's the only time I can ever remember something like that so I have a very warm feeling indeed for Shackleton and for his hut and I really believe Shackleton's hut must be preserved.

"Shackleton has always been my hero. I still admire enormously his courage and skill in moments of danger."

The hut is listed on the World Monuments Fund's 100 most endangered sites.

It is one of the few remaining buildings built on the frozen continent during the golden age of Antarctic exploration at the start of last century.

The building was prefabricated in England and was shipped to the Antarctic on the Nimrod and rebuilt on the site.

Apart from cramped living quarters for 14 men, the building contained dog kennels, stables for ponies, a meteorological station and a partially constructed laboratory.

The stove used for heating and cooking is still intact. Vast stores of tinned and dried food - everything from mock-turtle soup to raspberries - have remained at the site for nearly a century.

Clothing and scientific instruments are also among the artefacts at the site.

Five international experts led by Kiwi Nigel Watson, executive director of the New Zealand-based Antarctic Heritage Trust, are working at the site.

A $145,475 grant from American Express is helping to pay for the conservation work.

American Express spokesman Craig Dowling said the experts were racing against time as extreme weather constantly threatened the wooden hut's existence, built with no expectation of surviving beyond the initial mission.

"The Antarctic summer is short. [There is] a small window of opportunity in which to work, probably only a month depending on weather conditions," Mr Dowling said.

"It's not a project that can be completed in one summer and the conservation will be an ongoing project."

The hut was built for Shackleton's 1907-09 British Antarctic expedition when he led an attempt on the South Pole.

Shackleton turned his team back just 156km from their destination - the furthest south anyone had been at that time - when bad weather and dwindling supplies threatened their safe return.

He died on South Georgia Island in 1922 attempting to circumnavigate the Antarctic.